This invention relates generally to combined cycle power generation systems and more specifically, to methods and apparatus for fast starting and loading such systems.
As is well known in the art, combined cycle power systems include one or more gas turbines and heat recovery steam generators (HRSG's) and a steam turbine. Traditional combined cycle system startup procedures include low load holds of the gas turbine and restrictions on the gas turbine loading rate to control the rate of increase in steam temperature. These holds and restrictions contribute to air emissions during the startup event, may increase starting and loading time, and may increase fuel consumption during starting and loading.
More specifically, with combined cycle systems during starting and loading, and prior to the gas turbine achieving full load, the gas turbine is put on a hold until the temperature of the steam generated by the HRSG matches the steam turbine high pressure and intermediate pressure bowl metal temperature and/or the HRSG warms at an allowable rate and/or the HRSG is warmed up to the point of being ready for fuel heating. By holding the gas turbine at low load, the gas turbine operates at a low efficiency and with high exhaust emissions.
Such traditional starting procedures have been tolerated at least in part because in the past, startups were infrequent. With day to night power price swings, however, such startups have become more frequent.